The present invention relates to an automatic chemical analyzer which automatically performs a chemical analysis of samples.
Most of the conventional automatic chemical analyzers are of a multi-channel, multi-item type. The recent tendency has been toward a single-channel, multi-item analytic type, due to the demand that medical expenses be reduced, and, correspondingly, the cost of medical analysis be lowered. Therefore, demand is made for the development of an analyzer which can decrease the waste of reagents required for chemical analysis as much as possible.
A random-access method is known which can minimize the waste of reagents. This method is to distribute the reagent, which is necessary for analyzing a sample, to reaction tubes containing the sample. Generally, a nozzle is used to draw a required amount of the reagent and pipette this amount into the reaction tubes. This method can save reagents, unlike the conventional method wherein a reagent is poured from a container into the reaction tubes through a tube.
The random-access method can be classified into two categories. The method of the first category comprises the steps of moving reagent vessels in a circle, bringing the vessel containing any desired reagent to a predetermined position, withdrawing the reagent from the vessel by a nozzle at said position, transporting the nozzle to the required reagent-pipetting position, and pouring the reagent from the nozzle into the reaction tube located in said pipetting position. In the method of the second category, vessels containing different reagents are fixed at positions. This method comprises the steps of transporting a nozzle to one vessel containing the desired reagent, drawing the reagent from the vessel by the nozzle, bringing the nozzle to a reaction tube, and pouring the reagent from the nozzle into the reaction tube. The random-access method of the first category is predominantly used due to its high operability and efficiency.
The random-access method of the first category will now be described in detail, with reference to FIG. 1 which shows a conventional automatic analyzer. A number of reaction tubes 2 are set in first circle 4. They are intermittently transported along circle 4, for a predetermined pitch (one rotation+one pitch) at each time. A sample has been pipetted into the reaction tubes by a sampling nozzle (not shown). A plurality of reagent containers 6 are set in second circle 8 located adjacent to first circle 4, and are transported in second circle 8. Reagent-pipetting nozzle 10 is held by arm 12. As arm 12 rotates, nozzle 10 moves in arc 14 bridging both circular paths 4 and 8. When tube 2 containing a desired sample reaches reagent-pipetting position 16, reagent vessel 6 containing the reagent, which should be reacted with the sample to analyze the sample, is located in reagent-drawing position 18. A prescribed amount of the reagent is drawn from vessel 6 by nozzle 10 at position 18. Then, arm 12 is rotated, thus bringing nozzle 10 to position 16, where the reagent is poured from nozzle 10 into reaction tube 2. The reagent thereby starts reacting with the sample within reaction tube 2. Upon lapse of a predetermined period, the reaction condition within tube 2 is detected by colorimeter 20. More specifically, lens 24 focuses the light emitted from lamp 22 on reaction tube 2. The light passing through tube 2 passes through slit 26 and is reflected by concave grating 28, and reaches light-receiving element 30.
Recently, a clinical examination, involving a large variety of analyses, i.e., biochemical analysis, serum analysis, and medicine analysis, and the like, is performed by one and the same chemical analyzer. Therefore, an automatic random-access chemical analyzer is demanded which can quickly carry out such a clinical examination.
In order to accomplish a high-speed examination, numerous analyses must be carried out within a short time. When various analyses are performed at high speed, reagents are consumed in great quantities. Hence, in the conventional automatic chemical analyzer, it is necessary to use many reagent vessels for storing at least a one-day requirement of each reagent. The reagent storage will inevitably become expansive. Thus, it takes a long time to transport the vessel containing the desired reagent to the reagent-drawing position. Consequently, the pipetting of a reagent is slowed down, and a high-speed clinical examination cannot be accomplished. Further, the more analysis items, the more reagent vessels, including those containing seldom required ones, must be arranged. Hence, the reagent storage must be even larger.